MONTPELIER — A lawyer for the Vermont Yankee nuclear plant’s owner told the state Supreme Court on Wednesday it should dismiss a complaint that the plant has been disobeying orders from state utility regulators and should be shut down.

The arguments before the Vermont Supreme Court are just the latest in a long series of fights involving regulators, lawmakers and plant owner Entergy Corp. At issue this time is a clause in Entergy’s 2002 purchase agreement for the plant over a 2012 deadline for a new state permit.

Entergy lawyer Kathleen Sullivan disputed two rulings by the Public Service Board last year that the plant had been operating since March 21 in violation of the 10-year-old agreement with the state that it would shut down by that date if it didn’t have a new state permit.

Brice Simon, a lawyer for the anti-nuclear New England Coalition, told the justices he had decided to bring the group’s complaint to them because going to the Public Service Board “probably is futile.” He said the board “already has issued multiple orders finding that Entergy is in violation” of its 2002 order approving New Orleans-based Entergy’s purchase of Vermont Yankee from a group of New England utilities.

In the orders Simon referred to, the board stopped short of ordering the plant to shut down immediately, but made clear it would consider Entergy’s actions as it decides whether to grant the company’s request for a new state permit to operate until 2032. The Nuclear Regulatory Commission renewed Vermont Yankee’s federal license for that 20-year period in 2011.

The plant’s continued operation has been the subject of much legal and legislative wrangling.

Entergy’s attorney blamed the plant’s inability to get a new state permit on interference by the Legislature, which had passed two laws saying Vermont Yankee needed a green light from lawmakers in addition to the NRC and the Public Service Board. The Senate then denied the plant permission to continue operations while the matter never saw action in the House.

After it got its new NRC license, Entergy sued the state in U.S. District Court in Brattleboro, where a judge last January ruled that the Legislature had overstepped its bounds.

That put the question of the plant’s future back before the Public Service Board, where it had been before the Legislature’s involvement. While pre-empted from ruling on safety, the board maintains jurisdiction over the impacts of Vermont Yankee on the state’s environment and utility economics. Meanwhile, Vermont Yankee has kept operating, past the expiration of its initial state and federal licenses on its 40th birthday last March.

The Public Service Board raised the alarm in decisions in March and November that the plant’s continued operation appeared to violate part of a 2002 order approving Entergy’s purchase of Vermont Yankee. The agreement said the plant would stop operating if it did not get a new state permit before its 40th birthday.

A provision in Vermont law allows parties to cases before the Public Service Board to petition the Supreme Court if they feel board orders are not being adequately enforced. The anti-nuclear group New England Coalition, which had been a party to the 2002 PSB case on the sale of Vermont Yankee to Entergy, seized on that rarely used section of law last month, asking the court to shut Vermont Yankee down based on the sale agreement.

Wednesday’s hearing was on a request by Entergy to dismiss that complaint. The company argued that state law allows the plant to continue operating under its old license while its renewal is pending before the Public Service Board.

The only just outcome of the board process would be a win for Entergy, Sullivan said. “If they shut us down after this hearing they will be in defiance of Vermont law and of the District Court in Brattleboro. So they can do it, but it would be unlawful.”